A circuit called a 'TWIN-T" oscillator, one transistor, two capsand two resistors. and I recall that the output isvery nearly a sine wave. You could build one for eachtone or maybe just switch RC values around. Any ARRLhandbook in the last 40 years should have the circuitor find it on Google. Might cost $5.00 to make if youdon't have a junk box.

A telephone touch-tone pad generates two separate audio frequencies when you use it. The phone type has about 0 dBm output. And if you design around a VHF mic with internal pad the levels might be near what you need.

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